Objective The aim of the study was to evaluate the clinical efficacy of Oratest in detecting oral mucosal le- sions.Methods Sixty patients with oral mucosal lesions that were suspected as carcinoma or premalignant lesions were divided into two groups randomly. The lesionswere stainedwithOratest bytopical application in one group and rinse application in another group. Staining results were recorded and compared with the pathological diagnosis.Results The sensitivity of Oratest stain to oral carcinoma and dysplasia were 93·9% and 42·9%, respectively. The difference between rinse application and local applica- tion showed no significance(P>0·01).Conclusion Oratest can be used as a method of diagnosing squamous cell carcinoma of oral mucosa, but its reliability in screening oral pre-malignant lesions is still uncertain.